This invention relates to an improved drive mechanism for a balloon tired motorcycle and more particularly to the rear wheel drive for such a vehicle which incorporates a drive shaft.
Recently, it has been proposed to construct motorcycles for off the road use that use large, low pressure balloon tires for at least their rear wheels. The use of such large low pressure tires gives added stability and advantages for the off the road use. However, when such a wide rear tire is used, there are certain difficulties in connection with driving the tire. If the engine, which is mounted on the frame, includes a chain drive for the rear wheel and the rear wheel is driven directly from a sprocket on the engine output shaft, the driving chain is positioned well outwardly of the longitudinal center line of the motorcycle and in the position where it may interfere with the rider's legs.
To offset the aforenoted disadvantage, it has been proposed to provide a two chain arrangement for driving the rear wheel. Such an arrangement is shown in copending application Ser. No. 632,717, filed July 20, 1984 in the name of Nobuaki Shiraishi, entitled "Offroad Running Motorcycle" and assigned to the same assignee as this application, and comprises an intermediate shaft that is supported on the trailing arm suspension of the rear wheel and which is driven from a first chain that is driven directly by the engine output shaft and which is positioned relatively close to the longitudinal center line of the motorcycle. The intermediate shaft, in turn, drives the rear wheel through a second chain that is positioned a substantially greater distance outwardly from the center line so as to clear the rear wheel. Although this arrangement has advantages, it also has certain defects.
When such a two chain arrangement is employed embodying an intermediate shaft, it becomes very difficult to provide a mechanism for adjusting the tension of both of the driving chains. That is, it is not possible to adjust both chains sufficiently with a single adjustment of the intermediate shaft and the adjusting structure, therefore, becomes complicated. In addition, the flight between the engine output shaft and the intermediate shaft is relatively short and thus the first driving chain undergoes considerable stresses because of this short length and the life of the first driving chain can be significantly shortened.
It is, therefore, a principal object of this invention to provide an improved driving arrangement for an off the road motorcycle embodying a balloon tired rear wheel.
It is a further object of this invention to provide an offset driving arrangment for the rear wheel of such a motorcycle and one that does not employ two driving chains.
It is a further object of this invention to provide an offset drive arrangement for the balloon tired rear wheel of an off the road motorcycle that incorporates a drive shaft.